This invention pertains to zinc rich coatings with improved corrosion resistance and more particularly to compositions containing thermoplastic polyhydroxyethers or thermosetting epoxy resins, and an organosilane or organosilane hydrolyzate. The composition can optionally contain one or more suspending agents to provide a more stable composition in storage.
Zinc rich coatings containing both thermoplastic polyhydroxyethers and aluminum trihydrate have been used for corrosion protection of metallic substrates. Being electricially conductive they can also be used where welding is used as a technique for joining metallic parts. This property lends itself well to the automobile industry where electrical spot welding is the preferred fabrication technique in the assembly of automotive components.
Replacing part of the older zinc pigment in the zinc rich compositions with aluminum trihydrate improved the salt spray resistance of thermoplastic polyhydroxy ether and other coatings on cold rolled steel.
However, even with these improved formulations some deficiencies still remained. Undesirable leach rates of zinc pigments and aluminum trihydrate in salt spray tests prompted a search for means to improve this property. Various surface active agents were investigated unsuccessfully.
It is therefore an object of this invention to provide a zinc rich coating composition with enhanced corrosion resistance for coated metallic substrates.
It is another object to provide metallic substrates with zinc rich coatings which have controlled leaching rates in the presence of salt and other aqueous sprays.
Other objects will become apparent to those skilled in the art upon a further reading of the specification.